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An electrical current of 700 A flows through a stainless steel cable having a diameter of 5 mm and an electrical resistance of 6 x 10-40/m (i.e., per meter of cable length). The cable is in an environment having a temperature of 30°C, and the total coefficient associated with convection and radiation between the cable and the environment is approximately 25 W/m²K. (a) If the cable is bare, what is its surface temperature? (b) If a very thin coating of electrical insulation isapplied to the cable, with a contact resistance of0.02 m² K/W, what are the insulation and cablesurface temperatures? (c) There is some concern about the ability of the insula-tion to withstand elevated temperatures. What thick-ness of this insulation (k = 0.5 W/m · K) will yield the lowest value of the maximum insulation temper-ature? What is the value of the maximum tempera-ture when this thickness is used?

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